Platform slewing gear of single-motor universal type crane-excavator



March 8. 1966 l. L. BERKMAN ETAL 3,238,722

' PLATFORM SLEWING' GEAR OF SINGLE-MOTOR UNIVERSAL TYPE CRANE-EXCAVATOR Filed sp'b. 24, 1953 awp/uvre /35 emma Mmm /28 5y paru Vall/e Meara:

United States Patent O 3,238,722 PLATFORM SLEWING GEAR F SlNGLE-MOTR UNVERSAL TYPE RANEEXCAVATOR Iosif Lvovich Berkman, Moscow, Alexander Anatolievich Boolanov, Reutovo, Alexander Vladimirovich Ranuev, Ivanteevka, and Alexey Sergeevich Rebrov, Alexander Viacheslavovich Roostanovich, and (Bleg Arkadievich Smirnov, Moscow, all in U.S.S.R., assignors to Vsesouzny Nauchno-Issledovatelsky Institute Stroitelnogo i Dorozhnogo Mashinostroenija Filed Sept. 24, 1963, Ser. No. 311,256

Claims. (Cl. 60-51) The present invention relates to a hydraulic drive for the platform slewing gear of a universal excavator, which requires changes in the mode of operation in dependence upon the particular equipment employed, such as excavating or hoisting means.

It is generally known that a recuperative-accumulative drive is most suitable for a universal crane-excavator having a hydraulically driven slewing gear in digging operations requiring rapid and economical platform slewing. This drive is specic in that during slewing operations along with the energy delivered by the pump, the hydraulic slewing motor is supplied with energy stored in the high-pressure hydraulic accumulator, while during braking the energy wasted for slewing is recuperated in part in the high-pressure accumulator.

Likewise, it is common knowledge that crane equipment, especially that used in assembly operations requiring accurate handling at minimum slewing speeds, is advantageously driven by a hydraulic slewing motor having smooth rotational speed control, for instance, by means of an adjustable speed motor or by throttling.

Since the operating equipment is adapted to be replaced on site, the hydraulic drive for the platform slewing gear must be enabled to be readily and suitably changed over from pump accumulative control to smooth speed control, in other words a provision should be made to rapidly change recuperative-accumulative operation to smooth speed control.

Although attempts have been made to provide a hydraulic drive for the platform slewing gear to meet the above requirements, they all, to the best of our knowledge, have failed to produce a positive result.

The attempt to ensure sutlicient reliability of the recuperative-accumulative hydraulic drive has also failed.

It has now been found that these problems can be solved if the hydraulic drive for the platform slewing gear in universal crane excavators embodies the means of the present invention.

In broad terms, the invention is intended for hydraulically driven, reversible slewing gears possessing great gyrating mass, wherein depending on the equipment used or other operating requirements the hydraulic drive is adapted for recuperative-accumulative operation or regular volumetric hydrodrive operation with smooth speed control.

In accordance with the preferred embodiment the inventors have created an improved hydraulic drive circuit to drive the platform slewing gear of universal crane excavators. The circuit ensures dependable recuperativeaccumulative operation of excavating machines and permits the switching over of the drive for hoisting oper-ations where speed is controlled by a pump or -a throttle.

The object of the present invention is to provide a reliable and eicient drive for the slewing gear which is adjusted for -both recuperative-accumulative operation and regular volumetric hydr-odrive operation with smooth speed control.

In connection with the above and other objects the invention is embodied in a hydraulic drive for the platform slewing gear in a universal crane-excavator for application with excavating and hoisting machines and is designed for recuperative-accumulative operation, combined with means enabling the drive to be switched over to volumetric hydrodrive operation featuring smooth speed control.

The recuperative-accumulative circuit preferably comprises electromagnetic pickups responsive to the capacity of the power and delivery hydraulic accumulators and actuating electrohydraulic Valves governing safety valves which serve to relieve the power and feed pumps in providing for a desired volume in the power and feed hydraulic accumulators.

The above drive design allows easy changeover from recuperative-accumulative control to smooth speed control, as for instance by disconnecting the drive from the power accumulator and recuperative valves by means of valves, and by disconnecting the electromagnetic pickups from the low-voltage line by means of switches.

Other objects and advantages of the invention will become apparent from the following description and the accompanying drawing showing the invention as embodied on the principal hydraulic circuit for the slewing gear of a universal crane excavator.

The illustrated hydraulic drive circuit for such a slewing gear, as shown in the drawing, comprises components including a Vpower pump 1, a feed pump 2, a hydraulic motor 3, for driving the slewing gear, not shown, a lter 4, a high-pressure power hydraulic accumulator 5, a lowpressure feed hydraulic accumulator 6, an electromagnetic pickup 7 sensing the power hydraulic accumulator filling, a Second electromagnetic pickup 8 sensing the lling of the feed hydraulic accumulator 6, an electrohydraulic valve 9, a second electrohydraulic valve 10, a highpressure safety valve 11, a second and low-pressure safety valve 12, high pressure control means 13,1ow-pressure control means 14, an electric switch 15, an electric switch 16, a valve 17, a second valve 18, a check valve 19, a second check valve 20, stop means or controllable valves 21, 22, 23, feed check valves 24, recuperative check valves 25, a tive-position manually operable distribution valve 26, a means 26 for actuating said valve, by-pass valves 27 and y28, a delivery slide valve 29, stop or control valve means 30, a tank 31, a throttle 32 with a controller 33, a high-pressure delivery p-ipeline or means 34 connecting the delivery side of .the pump 1 and the distribution valve 26, a low-pressure pipe means 35, 35 connecting the distribution valve 26 with the intake side of the pump 1, operating pipelines or means 36 and 37 of the hydraulic mot-or 3, ya second delivery pipeline 38 connecting the delivery side of the feed pump 2 with the low-pressure pipe 35, an intake pipeline 39 connecting the tank 31 with the intake side of the feed pump through the stop means 30, and other dra-in pipes identified by dotted lines in the drawing.

The throttle 32 and the control 33 are connected in the circuit whenever a constant output or non-adjustable output pump is used as the power pump 1.

The above hydraulic drive circuit for the slewing gear allows recuperative-accumulative operation with excavating machines and regular volumetric hydrodrive operation combined with platform rotation speed control in hoisting machines, thereby reducing time and power consumption in slewing excavating machines and ensuring a desired assembly speed of hoisting machines. Furthermore, it improves reliability of the recuperative-accumulative operation.

Recuperative-accumulative operation occurs with the valves 21, 22 and 23 open. The hydraulic pumps 1 and 2 are driven by the excavator motor (not shown). The pump 1 is supplied with hydraulic iluid from the feed Patented Meur'. 8, 1966 hydraulic accumulator 6 arranged in the lowpressure pipe 35 through the ilter 4, and further applies it under pressure to the power hydraulic accumulator through the delivery pipeline 34 across the check valve 19. The feed pump 2 compensates fluid displacement in the system and supplies the operating fluid from the tank 31 through the check valve 20 to the feed hydraulic accumlator 6.

The electromagnetic pickups sensing the lling of the hydraulic accumulatore 7 and 8 and the electrohydraulic valves 9 and 10 governing the control safety valves 11 and 12, serve to unload the pumps 1 and 2 when the hydraulic accumulators 5 and 6 are filled to the desired level. Meanwhile the check valves 19 and 20 do not permit unloading of the hydraulic accumulators.

The hydraulic power accumulator 5 is fully charged in the initial position, while the feed hydraulic accumulator 6 is discharged approximately to 3A of its full capacity (the remaining quarter serves to maintain pressure in the intake line 35).

The pressure in the feed hydraulic accumulator 6 is selected to be minimum in dependence upon resistance offered by the pipelines, yet sufcient to feed the hydratilic motor 3 in braking. The pressure in the high-pressure hydraulic accumulator 5 should be selected possible higher to reduce the rated capacity of the hydraulic accumulator 5 and, hence, the hydraulic accumulator 6, because the capacity of the latter is made slightly larger than that of the hydraulic accumulator 5. The power and feed pumps 1 and 2 are idling. The slide valve 26 of the distribution valve is then in the neutral position, as shown in the drawing.

The slide valve, hand-actuated by the operator, lits into tive positions, i.e., a neutral position, two extreme positions and two intermediate positions, as diagrammatically shown in the drawing.

The slide valve 26 of the distribution valve in the neutral position disconnects the operating pipings 36 and 37 of the hydraulic motor 3 from the delivery pipeline 34 and from the low-pressure pipe means 35, 35. In this position the operating fluid under high pressure is not applied to the hydraulic motor 3, while the feed check valves 24 arranged between the low-pressure pipe means 35 and the operating pipelines 36 and 37 of the hydraulic motor 3 supply low-pressure Huid to both sides or spaces of the hydraulic motor.

As a result, the hydraulic motor 3 does not rotate and successfully brakes external loads, for instance, wind or slanting.

With the slide valve of the distribution valve 26 set in one of the extreme positions, the delivery pipeline 34 communicates with one of the operating pipelines of the hydraulic motor 3, while the pipeline 35, 35 simultaneously communicates with the opposite operating pipeline of the hydraulic motor 3. The high-pressure fluid from the hydraulic accumulator 5 is enabled to arrive in the respective side of the hydraulic motor 3, while the fluid displaced from the opposite space of the hydraulic motor 3 is enabled to act against the low pressure in the pipe 35 and to arrive in the feed hydraulic accumulator 6. The hydraulic motor 3 throws the slewing platform directly or through a reducing gear (not shown) into the required speed. By virtue of the high-pressure uid stored in the power hydraulic accumulator 5, the slewing platform races at a materially greater speed than the speed ensured by the power pump 1. In slewing, the power hydraulic accumulator 5 is discharged while the hydraulic accumulator 6 charges, because the power pump 1 fails to take in all the fluid flowing into the low-pressure pipe means 35, 35.

With the slide valve 26 set in an intermediate position, the high-pressure delivery piping 34 does not communicate with any other pipeline, while the low-pressure pipe means 35, 35 communicates with one of the working pipelines of the hydraulic motor 3. Neither does the other operating pipeline of the hydraulic motor communicate with any other pipeline. The hydraulic motor 3 assumes the so-called floating condition, permitting its rotation under the external loads or slewing platform inertia approximately without resistance in the hydraulic component, because the respective side or space of the hydraulic motor 3 then communicates through the distribution valve 26 with the low-pressure pipe means 35, 35', while the other side or space is supplied through one of the feed check valves 24 with low-pressure fluid from the same low-pressure pipe means 35, 35. Therefore, with the platform racing at a desired speed, the slide valve handle can be moved to the intermediate position to ensure slow braking of inertia movement.

Energetic and rapid braking of the slewing platform is effected by returning the slide valve 26 to the neutral position. Since, due to inertia the slewing platform revolves for some time, the hydraulic motor 3 will deliver the operating Huid from the low-pressure space to the power hydraulic accumulator 5 through one of the recuperative check valves 25 arranged between the delivery pipeline 34 and each of the operating pipelines 36, 37 of the hydraulic motor 3. The low-pressure space of the hydraulic motor 3 will be intensely supplied from the feed accumulator 6 through the respective feed check valve 24 across the low-pressure pipe 35 and one of the operating pipings 36, 37 of the hydraulic motor 3. The power accumulator 5 will thus recuperate part of the energy spent to revolve the slewing platform.

It should be noted that rotation is identical in either direction.

As soon as the piston of the power hydraulic accumulator 5 has reached the upper most position signifying the full charge of the hydraulic accumulator, the charging electromagnetic pickup 7 closes the electric circuit of the electrohydraulic valve 9, whose slide valve shifts to drain the fluid from the space behind the damper of the safety valve 11, which actuates the power pump 1 to drain the Huid, i.e., to idle. The electromagnetic valve 7 again closes the circuit of the electrohydraulic valve 9 and loads the power pump 1 only after the piston in the power accumulator 5 has descended a certain distance.

The feed pump 2 is unloaded in a similar manner.

The parameters of the hydraulic accumulators 5 and 6 and the power pump 1 are selected so that the original position is ensured at a pre-set angle of the platform slewing (with a certain tolerance).

In meeting the above requirements, the average effective power consumed for turning does not exceed 25 percent of the power generally consumed for this movement with a friction drive employed.

The regular volumetric hydrodrive with smooth speed control is achieved by the closure of the valves 21, 22 and `23 (with the high-pressure hydraulic accumulator 5 and the recuperative valves 25 cut off from the hydraulic drive).

rIhe electromagnetic pickups 7 and 3 are then disconrligcted from the low voltage line by the switches 16 and To prevent breakdown of the stream under action of weight components (with the machine inclined during platform slewing) or wind, a delivery slide valve 29 is used which is governed by the pressure in line 35, 35.

The slewing speed is adjusted by changing the efficiency of the power pump 1. Yet, whenever a constant output pump is used, the slewing speed is controlled by a throttle 32 interlocked ywith `the slide valve 26 and furnished with :a controller 33.

Although the present invention has been described in connection with the preferred embodiment, it will be apparent lthat changes `and variations may occur wit-hin the scope and spirit of the invention, and this will readily be understood by those skilled in the art.

These changes and variations are believed to be within the idea .and scope of the invention and the appended claims.

What we claim is:

1. A hydraulic drive for platform slewing gear of a universal excavator comprising Ia power pump adaptedto be driven by the excavator motor, a hydraulic motor for driving such ,a slewing gear, a high-pressure hydraulic accumulator, a low-pressure hydraulic accumulator, a live-position distribution valve, a low-pressure pipe means connecting said distribution valve with said low-pressure hydraulic accumulator and With the intake side of said power pump, a highapressure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and with said distribution valve; two pipe means for said hydraulic motor connecting said distribution valve with the opposite sides of said hydraulic motor; a safety valve limiting the differential pressure in said delivery and low-pressure pipe means; a means to move said distribution valve at the operators will to one `of live possible positions, namely, a neutral position lin which the lfour above-mentioned pipe means that are coupled to said live-position distrib-ution valve are not inter-communicated; two extreme positions in which said delivery pipe means communicates with one of said hydraulic motor pipe means, while said low-pressure pipe means communicates with the opposite pipe means of the hydraulic motor, and two intermediate positions in which said delivery pipe -means `and one of s-aid hydraulic motor pipe means do not communicate with each other and with the other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away :from each of said hydraulic motor pipe means towards said delivery pipe means and blocking fluid ow in the opposite direction; and feed check valves opening for passage of the operating fluid away from said lowpressure pipe means towards each -of said hydraulic motor pipe means and blocking iiuid flow in the opposite direction.

2. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, la high-pressure hydropneumatic accumulato-r, `a low-pressure hydropneumatic accumulator, a tive-position distribution valve, a lowpressure pipe means connecting said distribution valve 'with said low-pressure hydropneumatic laccumulator and with the intake side of said power pump, a high-pressure delivery pipe means connecting the delivery side of said power pump with said high-prsure hydropneumatic accumulator and with said distribution valve, two pipe means for said hydraulic motor connecting said distribution valve with the opposite sides of said hydraulic motor, a lsafety valve limiting the differential pressure in said delivery Iand low-pressure pipe means, a means to move said distribution valve at the operators will to one of five possible positions, namely, a neutral position -in which the above-mentioned four pipe means that are coupled to said live-position distribution valve do not communicate with each other, two extreme positions in which said delivery pipeline communicates with one of said pipe means for said hydraulic motor, `while ysaid low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, and two intermediate positions in which said delivery [pipe means and one of said pipe means for said hydraulic motor do not communicate with each other and with the other said pipe me-ans, while said low-pressure .pipe means communicate with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating iluid away from each of said hydraulic motor pipe means towards said delivery pipe means 'and blocking fluid flow in the opposite direction, feed check valves opening -for passage 6. of the operating fluid :away from said low-pressure pipe me-ans towards each of said hydraulic motor pipe means and blocking uid flow in the opposoite direction, and a means for purifying the operating fluid arranged in said low-pressure pipe means at a point between said lowpiressure hydropneumatic accumulator and said power pump.

3. A hydraulic drive for the platform slewing gear in a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, a high-pressure hydraulic accumulator, -a low-.pressure hydraulic accumulator, a five-position distribution valve, a low-pressure pipe means connecting said distribution valve with said low-pressure hydraulic accumulator and with the intake side of said power pump, a high-presure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and with said disv tribution valve, two hyd-raulic motor pipe means connectling said distribution valve with the opposite sides of said hydraulic motor, a safety valve limiting the differential pressure in said delivery and low-pressure pipe means, a means to set said distribution valve -at the operators will to one lof five possible positions, namely, a neutral position in which the four pipe means coupled to said distribution valve are not intercommunicated, two eXtreme positions in which said delivery pipe means communicates with one of the said hydraulic motor pipe means, while said lo-w-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, and two intermediate positions in which said delivery pipe means and one of said hydraulic motor pipe means do not communicate with each other and with the other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valve means opening for passage of the operating iluid away from each of said hydraul-ic motor pipe means towards said delivery pipe mean-s and blocking iluid flow in the opposite direction, feed check valves opening for passage of the operating fluid away from said low-pressure pipe means towards each of said hydraulic motor pipelines and blocking uid flow in the Opposite direction, control means for disconnecting said highpressure hydraulic accumulator arranged in said delivery pipe means to block passage of the operating uid through said recuperative check valves and to interlock said lowpressure pipe means at a point between said distribution valve and the connection of said feed check valves, a delivery slide v-alve lay-passing the interlocked portion of said low-pressure pipe means and operable from said delivery pipe means and interrupting drain from said distribution valve at Ia preset minimum diierential pressure of the operating uid in said delivery .pipe means exceeding the operating iluid pressure in said low-pressure pipe means.

4. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, a high-pressure hydraulic accumulator, .a low-pressure hydraulic accumulator, a fiveposition distribution valve, a low-pressure pipe means connecting said distribution valve with said low-pressure hydraulic accumulator andthe intake side of said power pump, a high-pressure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and with said distribution valve, two hydraulic motor pipe means connecting said distribution valve with the opposite sides of said hydraulic motor, a safety valve limiting the diierential pressure in said delivery and low-pressure pipe means, a means to set said distribution Valve at the operators will to one of ve possible positions, namely, a neutral position in which the four pipe means coupled to said distribution valve are not intercommunicated, two extreme positions in which said delivery pipe means communicates with one of said hydraulic motor pip-e means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, and two intermediate positions in which said delivery pipe means and one of said hydraulic motor pipe means do not communicate with each other and with other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away from each of said hydraulic motor pipe means towards said delivery pipe means and blocking fluid flow in the opposite direction, feed check valves opening for passage of the operating fluid away from said low-pressure pipe means towards each of said hydraulic motor pipe means and blocking fluid reversal in the opposite direction, stop means for d1sconnecting said lhigh-pressure hydraulic accumulator provided `in said delivery pipe means to block passage of the operating fluid through said recuperative check valves and to interlock said low-pressure pipe means at a point between said distribution valve and the connection of said feed check valves, a delivery slide valve by-passing the interlocked portion of said low-pressure pipe means and operable from said delivery pipe means to interrupt drain from said distribution valve at a pre-set minimum differential pressure of the operating7 fluid in said delivery pipe means exceedng the operating fluid pressure in said lowpressure pipe means, by-pass valves connected to each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means at the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said by-pass valve.

5. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, a high-pressure hydraulic accumulator, a low-pressure hydraulic accumulator, a five-position distribution valve, a low-pressure pipe means connecting said distribution valve with said low-pressure hydraulic accumulator and the intake side of said power pump, a high-pressure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and said distribution valve, two hydraulic motor pipe means connecting said distribution valve with the opposite sides `of said hydraulic motor, a safety valve limiting the differential pressure in said delivery and low-pressure pipe means, a means to set said distribution valve at the operators will to one of five possible positions, namely, a neutral position in which the four pipe means coupled to said distributon valve are not intercommunicated, two extreme positions in which said delivery pipe means communicates with one of said hydraulic motor pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, and two intermediate positions in which said delivery pipe means and one of said hydraulic motor pipe means do not communicate with each other and with the other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away from each of said hydraulic motor pipe means towards said delivery pipe means and blocking fluid flow in the opposite direction, feed check valves opening for passage of the operating fluid away from said low-pressure pipe means twards each of said hydraulic motor pipe means and blocking fluid flow in the opposite direction, stop means for disconnecting said 4high pressure hydraulic accumulator arranged in said delivery pipe means for blocking passage of the operating fluid through said recuperative check valves and to interlock said low-pressure pipe means at a point ybetween said distribution valve and the connection of said feed check valves, a delivery slide valve bypassing the interlocked portion of said low-pressure pipe means and operable from said delivery pipe means to interrupt drain from said distribution valve at a pre-set minimum differential pressure of the operating fluid in said delivery pipe means exceeding the operating fluid pressure in said flow-pressure pipe means, by-pass valves connected to each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means upon the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said by-pass valves, and a normally 'open throttle and a control means therefor arranged between said delivery and low-pressure pipe means to permit switching over to crane operation.

6. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a Islewing gear, a high-pressure hydraulic accumulator, a low-pressure hydraulic accumulator, a five-position distribution valve, a low-pressure pipe means connecting said distribution valve with said lowpressure hydraulic accumulator and the intake side of said power pump; a high-pressure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and said distribution valve, two hydraulic motor pipe means connecting said distribution valve with the opposite sides of said hydraulic motor, a safety valve limiting the differential pressure in said delivery and low-pressure pipe means, a means to set said distribution valve at the operators will to one of five possible positions, namely, a neutral position in which the four pipe means coupled to said distribution valve are not interconnected, two extreme positions in which said delivery pipe means communicates with one of said hydraulic motor pipe means of said hydraulic motor, and two intermediate positions in which said delivery pipe means and one of said hydraulic motor pipe means do not communicate with each other and with the other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away from each of said hydraulic motor pipe means towards said delivery pipe means and blocking fluid flow in the opposite direction, feed check valves opening for passage of the operating fluid away from said low-pressure pipe means towards each of said hydraulic motor pipe means and. blocking fluid flow in the opposite direction, a check valve mounted in said delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating fluid only away from the delivery side of said power pump towards said high-pressure hydraulic accumulator, and by-pass valves connected to each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means upon the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said by-pass valves.

7. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, a high-pressure hydraulic accumulator, a low-pressure hydraulic accumulator, a five-position distribution valve, a low-pressure pipe means connecting said distribution valve with said lowpressure hydraulic accumulator and the intake side of said power pump, a high-pressure delivery pipe means connecting the delivery side of said power pump with said high-pressure hydraulic accumulator and said distribution valve, two hydraulic motor pipe means connecting said distribution valve with opposite sides of said hydraulic motor, a safety valve limiting the differential pressure in said delivery and low-pressure pipe means, a means to set said distribution valve at the operators will to one of five possible positions, namely, a neutral position in which the four pipe means coupled to said distribution valve are not interconnected, two extreme positions in which said delivery pipe means communicates with one of said hydraulic motor pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, and two intermediate positions in which said delivery pipe means and one of said hydraulic motor pipe means do not communicate with each `other and the other said pipe means, while said low-pressure pipe means communicates with the opposite pipe means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away from each of said hydraulic motor pipe means towards said delivery pipe means and blocking fluid flow in the opposite direction, feed check valves opening for passage of the operating fluid away from said low-pressure pipe means towards each of said hydraulic motor pipe means and blocking fluid iiow in the opposite direction, a check valve mounted in said delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating uid only away from the delivery side of said power pump towards said high-pressure hydraulic accumulator and a second safety valve connected to said delivery pipe means at a point between said check valve and the connection of said recuperative valves to limit the differential pressure between the point of the delivery pipe means where it is mounted and said low pressure pipe means. Y

8. A hydraulic drive for the platform slewing gear of a universal excavator as claimed -in claim 1 and further including a check valve mounted on the delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating fluid only away from the delivery side of said power pump towards said highpressure hydraulic accumulator, by-pass valves arranged in each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means upon the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said bypass valves, and a means to unload said power pump which directs the free flow from said power pump into said low-pressure pipe means when either the volume or the operating uid pressure in said high-pressure hydraulic accumulator have reached the pre-set value and reverses the ow from said power pump into said highpressure hydraulic accumulator upon decrease in either the pressure or volume of the operating iiuid in said highpressure hydraulic accumulator.

9. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and further including a check valve mounted on the delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating uid only away from the delivery side of said power pump towards said highpressure hydraulic accumulator, control means for disconnecting said high-pressure hydraulic accumulator arranged in said delivery pipe means to block passage of the operating fluid through said recuperative check valves and to interlock said low-pressure pipe means at a point between said distribution valve and the connection of said feed check valves, a delivery slide valve for by-passing the interlocked portion of said low-pressure pipe means, and operable from said delivery pipe means to interrupt iiow from said distribution valve upon the preset minimum differential pressure 4in said delivery pipe means exceeding the operating uid pressure in said low pressure pipe means and by-pass valves arranged in each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means upon the differential pressure of the operating uid in said hydraulic motor pipe means exceeding the reference pressure of said bypass valves.

' 10. A hydraulic drive for the platform slewing gear in a universal excavator as claimed in claim 9 and further including a normally open throttle valve and a controller therefor arranged between said delivery and low-pressure means to permit switching over to crane operation.

11. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and further including a check valve mounted in the delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating uid only away from the delivery side of said power pump towards said highpressure hydraulic accumulator, by-pass valves arranged in each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means to the opposite pipe means upon the differential pressure in said hydraulic motor pipe means exceeding the reference pressure of said by-pass valves, a means to unload said power pump which directs the free flow from said power pump into said low-pressure pipe means when the volume or operating fluid pressure in said highpressure hydraulic accumulator has reached the pre-set value and reverses the ow from said power pump into said high-pressure hydraulic accumulator upon decrease in the pressure or volume of the operating uid in said high-pressure hydraulic accumulator, control means for disconnecting the high-pressure hydraulic accumulator arranged in said delivery pipe means to block passage of the operating uid through said recuperative check valves and to interlock said low-pressure pipe means at the point between said distribution valve and the connection of said feed check valves, a delivery slide valve for bypassing the interlocked portion of said low-pressure pipe means and operable from said delivery pipe means to interrupt drain from said distribution valve at the preset minimum differential pressure of the operating iiuid in said delivery pipe means exceeding the operating uid pressure in said low-pressure pipe means.

12. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and an operating fluid tank means, drain pipe means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be driven by the excavator motor, a low-pressure delivery pipe means in said feed pump to communicate the delivery side of said feed pump with said drain pipe means, a feed motor intake piping connecting the intake side of said feed pump with said tank means, and a second safety valve for limiting the pressure in said delivery pipe means of said feed pump.

13. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and a check valve in said delivery pipe means between the connection of said safety valve and the connection of said highpressure hydraulic accumulator to pass the operating fluid only from the delivery side of said power pump towards said high-pressure hydraulic accumulator, a means to unload said power pump which directs the unobstructed liow from said power pump into said low-pressure pipe means when the volume or operating fluid pressure in said high-pressure hydraulic accumulator has reached a pre-set value and reverse the ow from said power pump into said high-pressure hydraulic accumulator upon decrease in the pressure or volume of the operating fluid in said high-pressure hydraulic accumulator, by-pass valves connected to each of said hydraulic -motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means into the opposite pipe means upon the differential pressure in said hydraulic motor pipe means exceeding the reference pressure of said bypass valves, an operating fluid tank means, drain pipe means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be actuated by the excavator motor, a lowpressure delivery pipe means to communicate the delivery side of said feed pump with said drain pipe means, an intake piping in said feed pump to communicate the intake side of said feed pump with said tank means and a second safety valve for limiting the pressure in said delivery pipe means of said feed pump.

14. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 13 and a second check valve mounted in the delivery pipe means of the feed pump between said second safety valve and said drain pipe means and an additional safety valve for limiting the pressure in said drain pipe.

15. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 13 and a second check valve mounted in said delivery pipeline means of said feed pump between said second safety valve and said drain pipe means, and means for unloading said feed pump which directs the unobstructed flow from said feed pump into said tank means when the volume or pressure of the operating fluid in said lowpressure hydraulic accumulator has reached pre-set values and reverses the iiow from said feed pump into said lowpressure hydraulic accumulator upon decrease in the ypressure or volume of the operating fluid in said lowpressure hydraulic accumulator.

L6. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and further including an operating uid tank means, drain pipeline means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be driven by the excavator motor, a lowpressure delivery pipeline means for said feed pump to communicate the delivery side of said feed pump with said low-pressure pipe means, an intake piping for said eed pump to communicate the intake side of said feed pump with said tank means, a second safety valve limiting the pressure in said delivery pipeline means of said feed pump, stop means disconnecting said high-pressure hydraulic accumulator arranged in said delivery pipe means to stop operating fluid passage through said recuperative check valves and to interlock said low-pressure pipe means at a point between said distribution valve and the connection of said feed check valves, a delivery slide valve by-passing the interlocked portion of said lowpressure pipe means and controllable from said delivery pipe means to interrupt drain from said distribution valve upon a pre-set minimum differential pressure of the operating uid in said delivery pipe means exceeding the operating fluid pressure in said low-pressure pipe means.

17. A hydraulic drive for the platform slewing gear of a universal excavator as claimed in claim 1 and a means to unload said power pump which directs the unobstructed flow from said power pump into said low pressure pipe means when the volume or pressure of the operating fluid in said high-pressure hydraulic accumulator has reached a pre-set value and reverses the flow from said power pump into said high-pressure hydraulic accumulator upon decrease in the pressure or volume of the operating fluid in said high-pressure hydraulic accumulator, an operating fluid tank means, drain pipe means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be driven by the excavator motor, a lowpressure delivery pipe means for `said feed pump to communicate the delivery side of said lfeed pump wit-h said low-pressure pipe means, an intake piping means for the feed pump to communicate the intake side of said feed pump with said Itank means, a second safety valve limiting the pressure in said delivery pipeline means of said feed pump, la check valve mounted in said delivery pipeline means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic accumulator to pass the operating fluid only away from ythe delivery side of said power pump towards said highpressure hydraulic accumulator, by-pass valves connected to each of said hydraulic motor pipe means to by-pass the operating uid from each of said hydraulic motor pipe means into the opposite pipe means upon the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said bypass valves, stop means disconnecting said high-pressure hydraulic accumulator arranged in said delivery pipe means to stop operating iiuid passage through said recuperative check valves and to interlock said low-pressure pipe means at -a point between said distribution valve and the connection of said feed check valves, and a delivery `slide valve by-passing the interlocked portion of said low-pressure pipe means and controllable from said dedivery pipe means to interrupt drain from said distribution valve at a pre-set minimum differential pressure of the operating iiuid in said delivery pipe means exceeding the operating fluid pressure in said low-pressure pipe means.

18. A hydraulic drive for the platform slewing gear for a `universal excavator as claimed in claim 17 and an additional check valve mounted in said delivery pipeline means of the feed pump between said second safety v-alve and said low-press-ure pipe means and yan -additional safety valve limiting the pressure in said low-pressure pipe means.

19. A hydraulic drive `for the platform slewing gear of a universal excavator as claimed in claim 1 and a check valve mounted in said delivery pipe means at a point between the connection of said safety valve and the connection of said high-pressure hydraulic laccumulator to pass the operating fluid only away from t-he delivery side of said power pump towards said high-pressure hydraulic accumulator, by-pass valves mounted on each of said hydraulic motor pipe means to by-pass the operating fluid from each of said hydraulic motor pipe means into the opposite pipe :means upon the differential pressure of the operating fluid in said hydraulic motor pipe means exceeding the reference pressure of said by-.pass valves, an operating fluid tank means, drain pipe means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be driven by the excavator motor, a low-pressure delivery pipe means for said feed pump to communicate the delivery side of said feed pump with said low-pressure drain pipe means, an intake piping for the feed pump to communicate the intake side of said feed pump with said tank means, a second safety valve limiting the pressure in said delivery pipe means of said feed pump, a second check valve mounted` in the delivery pipe means of said feed pump at a point between said second safety valve and said low-pressure pipe means, a means to unload said feed pump which directs the unobstructed ow from said feed pump into said tank means when the volume or pressure of the operating fluid in said low-pressure hydraulic laccumulator has reached a pre-set value and reverses the flow from said feed pump into said lowpressure hydraulic accumulator upon decrease in the pressure or volume of the operating uid in said lowpressure hydraulic accumulator, stop means disconnecting said high-pressure hydraulic accumulator arranged in said delivery pipe means to stop operating uid flow through said recuperative check valves and to interlock said lowpressure pipe means at a point between said distribution valve and the connection of said feed check valves, a delivery slide valve by-passing the interlocked portion of said low-pressure pipe means and controllable from said delivery pipe means to interrupt drain from said distribution valve upon a pre-set minimum differential pressure of the operating uid in said delivery pipe means exceedin-g the oper-ating fluid pressure in said low-pressure pipe means, and a means to unload said power pump which directs the unobstructed flow from said power pump into said low-pressure pipe means when the volume or pressure of the operating iiuid in said high-pressure hydraulic accumulator lhas reached the pre-set value and reverses the flow from said power pump into said high-pressure hydraulic accumulator upon 'decrease in the pressure of volume of the operating uid in said high-pressure hydraulic accumulator.

20. A hydraulic drive for the platform slewing gear of a universal excavator comprising a power pump adapted to be driven by the excavator motor, a hydraulic motor for driving such a slewing gear, a high-pressure hydropneumatic accumulator, :a low-pressure hydropneumatic accumulator, a five-position distribution valve, -a low-pressure pipe means connecting said distribution valve with said low-pressure hydropneumatic -accumulator and the intake side of said power pump, a high-pressure delivery pipe line means connecting the delivery side of said power pump with said high-pressure hydropneumatic accumulator and said ldistribution Valve, two hydraulic motor pipeline means connecting said distribution valve with opposite sides of said hydraulic motor, an electrohydraulically controlled safety valve limiting the differential pressure lin said delivery and low-pressure pipe line means, a means to set said distribution valve at the operators will to one of five possible positions, namely, a neutral position in which the four pipeline means Coupled to said distribution valve are not intercommunicated, two extreme positions in which said delivery pipeline means communicates with one of said hydraulic motor pipeline means, while said low-pressure pipe means communicates with the opposite pipeline means of said hydraulic motor, and two intermediate positions in which said delivery pipeline means and one of said hydraulic motor pipeline means do not communicate with each other and with the other said pipeline me-ans, while said low-pressure pipe means communicates with the opposite pipeline means of said hydraulic motor, recuperative check valves opening for passage of the operating fluid away from each of said hydraulic motor pipeline means towards said delivery pipeline means and blocking fluid ow in the opposite direction, feed check valves opening for passage of the operating iuid away from said lowpressure pipe means towards each of said hydraulic motor pipe line means and blocking fluid ow in the opposite direction, a check valve mounted in said delivery pipeline means at a point between the connection of said safety valve and the connection of said high-pressure hydropneumatic accumulator to pass the operating iiuid only away from the delivery side of said power pump towards said high-pressure hydropneumatic accumulator, stop means disconnecting said hi-gh-pressure hydropneumatic accumulator arranged in said delivery pipeline means to stop operating uid flow through said recuperative check valves and to interlock said low-pressure pipe means at a point between said distribution valve and the connection of Said feed check valves, a delivery slide Valve by-passing the interlocked portion of said lowpressure pipe means and controllable from said delivery pipeline means to interrupt low-pressure from said distribution valve upon a pre-set minimum differential pressure of the operating fluid in said delivery pipeline means exceeding the operating uid pressure in said low-pressure pipeline means, a normally open throttle valve with a controller arrange-d between said delivery and low-pressure pipeline means =to permit switchin-g over to crane operation, an electromagnetic volumetric pickup furnished in a space of said high-pressure hydropneumatic `accumulator to close the electric circuit of =a two-position electrohydraulic valve governing said distribution yvalve by connecting a space downstream of said safety v-alve with said low-pressure pipe means or a tank means, an operating fluid tank means, drain pipeline means connecting the drain side of said power pump and said hydraulic motor with said tank means, a feed pump adapted to be driven by the excavator moto-r, a low-pressure delivery pipeline means for said feed pump to communicate the delivery side of said feed pump with said drain pipe means, an intake piping for said feed pump to communicate the intake side of said feed pump with said tank means, a second safety valve limiting pressure in said delivery pipeline means of said feed pump, a second check valve mounted -in said delivery pipeline means of the feed pump at a point between said second safety valve and said drain pipe means, a second electromagnetic volumetric pickup furnished in a space of said low-pressure hydropneumatic accumulator to close the electric circuit of the second safety valve through connecting the Space downstream of -second safety valve with said tank means, a relieving pipeline means for said hi-gh-pressure hydropneumatic accumulator to communicate the ope-rating fluid space of said high-pressure hydropneumatic accumulator with said low-pressure pipe means or said tank means, stop means for stopping iluid flow through said relieving pipeline means of said high-pressure hydropneumatic accumulator, a relieving pipeline means for said low-pressure hydropneumatic accumulator communieating the operating fluid space of said low-pressure hydropneumatic accumulator with said tank means, a stop means blocking the fluid passage through said second relieving pipeline means, controls furnished in said delivery pipeline means and said low-pressure pipe means, a means to purify the openating fluid in said low-pressure pipe means at a point between said low-pressure hydropneumatic accumulator and said power pump and drain pipelines connecting the drain side of said power pump and said hydraulic motor with said low-pressure pipe means.

References Cited by the Examiner UNITED STATES PATENTS 2,555,427 6/ 1951 Trautman 60-51 2,687,011 8/ 1954 Frankel 60-51 2,802,336 8/ 1957 Ball 60--51 2,955,917 10/ 1960 Roberts et al, 60-50 X 2,972,863 2/ 1961 Hyde 60-51 SAMUEL LEVINE, Primary Examiner.

EDGAR W. GEOGHEGAN, IULIUS E. WEST,

Examiners. 

1. A HYDRAULIC DRIVE FOR PLATFORM SLEWING GEAR OF A UNIVERSAL EXCAVATOR COMPRISING A POWER PUMP ADAPTED TO BE DRIVEN BY THE EXCAVATOR MOTOR, A HYDRAULIC MOTOR FOR DRIVING SUCH A SLEWING GEAR, A HIGH-PRESURE HYDRAULIC ACCUMULATOR, A LOW-PRESSURE HYDRAULIC ACCUMULATOR, A FIVE-POSITION DISTRIBUTION VALVE, A LOW-PRESSURE PIPE MEANS CONNECTING SAID DISTRIBUTION VALVE WITH SAID LOW-PRESSURE HYDRAULIC ACCUMULATOR AND WITH THE INTAKE SIDE OF SAID POWER PUMP, A HIGH-PRESSURE DELIVERY PIPE MEANS CONNECTING THE DELIVERY OF SIDE OF SAID POWER PUMP WITH SAID HIGH-PRESSURE HYDRAULIC ACCUMULATOR AND WITH SAID DISTRIBUTION VALVE; TWO PIPE MEANS FOR SAID HYDRAULIC MOTOR CONNECTING SAID DISTRIBUTION VALVE WITH THE OPPOSITE SIDES OF SAID HYDRAULIC MOTOR; A SAFETY VELVE LIMITING THE DIFFERENTIAL PRESSURE IN SAID DELIVERY AND LOW-PRESSURE PIPE MEANS; A MEANS TO MOVE SAID DISTRIBUTION VALVE AT THE OPERATOR''S WILL TO ONE OF FIVE POSSIBLE POSITIONS, NAMELY, A NEUTRAL POSITION IN WHICH THE FOUR ABOVE-MENTIONED PIPE MEANS THAT ARE COUPLED TO SAID FIVE-POSITION DISTRIBUTION VALVE ARE NOT INTER-COMMUNICATED; TWO EXTREME POSITIONS IN WHICH SAID DELIVERY PIPE MEANS COMMUNICATES WITH ONE OF SAID HYDRAULIC MOTOR PIPE MEANS, WHILE SAID LOW-PRESSURE PIPE MEANS COMMUNICATES WITH THE OPPOSITE PIPE MEANS OF THE HYDRAULIC MOTOR, AND TWO INTERMEDIATE POSITIONS IN WHICH SAID DELIVERY PIPE MEANS AND ONE OF SAID HYDRAULIC MOTOR PIPE MEANS DO NOT COMMUNICATE WITH EACH OTHER AND WITH THE OTHER SAID PIPE MEANS, WHILE SAID LOW-PRESSURE PIPE MEANS COMMUNICATES WITH THE OPPOS- 